The present invention is discussed in the context of high definition television (HDTV) a digital medium, since it provides substantial benefit in terms of efficient use of broadcast band spectrum and division of geographical territory into which signals are broadcast in to distinguishable primary and lower tier broadcast areas. As further articulated below, more generalized use in over-the-air broadcasting is available.
Analog TV broadcast stations currently are each assigned a bandwidth of 6 MHz, and an operating range limited to the line-of-sight distance (up to 55.5 miles), which equates to the distance that a vhf or uhf signal travels with a transmitting antenna elevated to the practical heights of antenna towers. Each broadcast station maintains a transmitter site within its licensed market area, with the locations typically on the highest elevations of the area, to permit maximum coverage with the lowest investment in property and antenna tower structure. Because of the random location of transmitting towers, TV viewers receive less than optimum signals from over-the-air broadcasters, due to misalignment of the viewer's antenna or due to the low gain of the viewer's antenna, necessary to allow for receiving multiple stations without constantly repositioning the antenna. Low signal strength and low signal to noise ratios due to subscriber antenna positioning and to receiver antenna gain require more elegant processing to compensate for these shortcomings. In the future, anticipated interference between analog and digital transmission within the same frequency bands should provide further reception degradation, as well as allowing the most efficient use of the available spectrum.
A worldwide transition from analog television broadcasting to digital broadcasting will take place. Under a current model for the transition in the United States, HDTV spectrum has been given to incumbent broadcasters at no cost to the broadcasters. The transition will have a duration of 15 years. Also, HDTV frequency allocation will be 6 MHz for each licensed station, occupying the guard band or taboo channels between current analog channels for the 15 year transition period. When analog transmission is discontinued, current analog TV channels 2 through 13 will be reallocated for other non-TV use. The current plan of the United States Federal Communications Commission, FCC, is to allocate broadcast TV bandwidth for HDTV use in the same manner as was used for analog TV, providing a discrete 6 MHz assignment to each broadcaster. There are current geographical constraints on analog broadcasting. A television channel may used to cover a radius of up to 55.5 miles, transmitted from existing transmitting sites. The same frequency may then not then be re-used for a minimum of 155 miles. These same constraints are contemplated under the current United States model for the transition.
The current HDTV implementation plan is to provide each of the incumbent 1500 analog based TV stations a free license for use of 6 MHz of bandwidth designated for HDTV use, that will be located in the guard band adjacent to the existing 6 MHz channel that is now licensed for analog transmission. Starting in May of 1999, and extending through December of 2005, both analog and digital HDTV signals will be transmitted from the same transmitter site as is currently used for analog. Under the current schedule, on Jan. 1, 2006, all analog TV transmission will cease, ending the analog era in broadcast TV history. However, the model does not improve on the historic TV broadcast licensing methodology that was put into place 50 years ago, when the frequency band allocations did not have to be made to the exclusion of others services, as is the case in 1997.
The 250 million analog TV sets that currently exist in the United States will not be able to receive the digital over-the-air signals and will become obsolete with the introduction of digitally TV transmission equipment. Digital TV sets to receive the HDTV signal are estimated to cost are in the range of $2000 for each set by the year 2006. This will result in the cost to the U.S. public that will approach $500 billion for receiving equipment alone under the current model. Estimates are that digital TV broadcast stations will cost $500 to $600 thousand each, a major burden for the 1500 broadcast stations that will need to be converted to handle digital transmissions, for a total of $750 to $900 million. Add to these equipment costs the significant software costs for converting the entire analog based film libraries to the HDTV digital format, will reveal the total cost impact for moving from analog to digital HDTV within a period of one and a half decades. This financial drain on the U.S. economy represents the largest single cost element that will be imposed on the U.S. population over the next several decades. To put this into prospective, the cost impact amounts to 6 to 7 times the total cost for financing and administering the Marshall plan following World War II. The Marshall Plan was funded by sale of surplus military equipment. Here, funding must by underwritten by private citizens and companies.
For all the huge capital expenditures the current model will require, no significant improvement in the broadcasting infrastructure. The program for allocating TV licenses and frequencies was established in the mid 1940s and early 1950s. At that time, the electromagnetic spectrum was not considered a scarce resource. Bandwidth efficient methodologies had yet to be developed. Despite a large body of knowledge that has been developed over the past fifty years for more efficiently utilizing the spectrum, the current model for allocating spectrum for the introducing HDTV is based upon the original frequency allocation plan for and ignores technological advancements that have occurred since then.